This invention refers to a method of activating large quantities of security elements to electronically protect articles, to a large-scale activator for the activation of such security elements, and to the security elements themselves.
In this connection it should be mentioned that the individual security elements have a magnetic material with high permeability and low coercive force (magnetically soft material) and a magnetic material with low permeability and high coercive force (magnetically semi-hard or hard material). The magnetically soft material is ordinarily excited by application of an alternating magnetic field in a query zone for remission of a characteristic signal. This characteristic signal can be suppressed if the magnetically semi-hard or hard material is in a remanent magnetization state after a correspondingly high magnetic field has been applied.
Security elements of the type described above are preferably used in the field of electronic article protection in department stores and warehouses. A particularly advantageous embodiment of a security element has been published in EP 0 295 028 B1. So-called thin-film security elements are described in this patent specification. These elements are comprised of a thin layer—preferably in the μm range—of magnetically soft material. The layer is applied to a carrier substrate, for example by means of a physical deposition process under vacuum conditions.
Thin-film security elements have an anisotropic structure. Anisotropic means that the magnetically soft layer of which the thin-film security elements are made has a preferred axis. In practice, the anisotropic structure reveals itself in that the characteristic signal remitted by the thin-film security element in response to a query field is at a maximum when the query field and the preferred axis are parallel to one another; on the other hand, the signal disappears when the preferred axis and the query field are perpendicular to one another.
Analogous behavior is also displayed by the so-called strip elements comprised of a strip of magnetically soft material. Here, too, the characteristic signal is at a maximum when the query field and the strips are parallel to one another, and it disappears when they are perpendicular. Moreover, the strip element can also be comprised of a drawn wire.
A plurality of different methods for the detection of security elements in the query zone have been publicized. The detection apparatus proposed in EP 123 586 B is one example.
For the deactivation of a thin-film security element following proper payment for the protected article, a punched foil—for instance of a magnetically hard material such as nickel—is provided on the magnetically soft material. In the case of strip elements, segments of a magnetically semi-hard or hard material are arranged in close proximity to the magnetically soft strip or even directly on the strips themselves.
In both cases, the remagnetized deactivation material generates a stray field that pre-magnetizes the magnetically soft material in such a manner that it is no longer detected in the query zone. To achieve a reliable deactivation it is necessary for the deactivation material to be converted to a defined magnetized state (remanence) that ensures maximum magnetization and therefore a maximum stray field.
At present, the security elements mentioned repeatedly above are generally supplied to the user in an activated state.
However, since only a portion of industry and retail businesses have systems for the detection and deactivation of the electromagnetic security elements described here, the manufacturers and distributors of such security elements are becoming increasingly interested in shipping the security elements in the deactivated state, i.e. with remanent magnetically hard deactivation material. Interest in such a procedure has grown since the Institut für Distributions- und Handelslogistik (Institute of Distribution and Trade Logisitics) in D-44227 Dortmund has been advocating the deactivation of such security elements with one hundred percent certainty, while a ninety-eight percent success rate is considered adequate for the activation of the security elements. These requirements have meanwhile also been set forth in the VDI (Association of German Engineers) Guideline 4471, sheet 1.
Due to the state of affairs described above, it appears to be advantageous to carry out the activation in central distribution sites in which it is known which purchasers require activated or deactivated security elements. In this connection it would be advantageous to be able to activate entire palettes of security elements at a time.
The activation of such large quantities of security elements is not possible with today's state of the art. Therefore, up to now, this procedure has been too costly. At present it is only possible to activate small quantities of security elements, for example in a tunnel demagnetization device for demagnetizing workpieces. These tunnel demagnetization devices generally have a coil which generates an alternating magnetic field for demagnetization of the workpieces. The amplitude of this alternating field diminishes during the demagnetizing process, so that the workpiece is successively demagnetized. However, due to the strong dependence of the action of the magnetic field on the distance between workpiece and coil, the dimensions of the tunnel in which the workpieces are demagnetized are severely limited. For example, the company Bakker Magnetics b.v., Sciencepark Eindhoven 5502 in 5692 E L Son, the Netherlands, offers such a device under article number BM 70.200. This device has a demagnetizing tunnel measuring 220 (length)×150 (width)×60 (height)mm3. To produce a magnetic flux within this tunnel which is adequate to reliably demagnetize the workpieces, the device requires an electric power of 1050 watts. If the device is operated with 220 v alternating current, a maximum effective current of approximately 5 A therefore results. In the case of extended periods of operation this very quickly leads to coil overheating and hinders prolonged running of the device.
Moreover, the demagnetization of the security elements in such a tunnel demagnetization device is often not reliable enough. One reason for this drawback, for example, is that even a small angle between the magnetic field of the demagnetization device and the security element or elements to be activated prevents complete demagnetization of their magnetically hard components, so that the security elements in question remain in the deactivated state.